Industrial machines, such as bonding apparatuses used in semiconductor manufacturing processes and various forming machines that perform press forming or powder forming, perform processing while a pressurizing head, which is a motor-driven mechanical load, applies a force on a workpiece, which is a subject to be pressurized. In the case of the bonding apparatuses, an electronic substrate, a film, an IC chip, a semiconductor package, or a wafer corresponds to the workpiece, and in the case of the forming machines, metal, powder in a mold, or resin to be formed corresponds to the workpiece. Such bonding apparatuses or forming machines include a sensor, typified by a load cell, that detects force or pressure in a pressurizing head or in a mechanism that drives the pressurizing head to control the motion of a motor such that the force or pressure applied to various workpieces achieves a desired value. The motor here is an electric motor for driving the pressurizing head.
The industrial machines described above first position the pressurizing head in a place away from the workpiece and not in contact with the workpiece and perform a feeding action such that the pressurizing head approaches the workpiece. When the pressurizing head comes in contact with the workpiece, then, the industrial machines described above perform a pressurizing action on the basis of a signal detected by the sensor that detects the force or pressure. Thus, the industrial machines described above need control to switch from the feeding action to the pressurizing action by an appropriate means. Generating a shock or vibration during the switching is of course not preferable for the machines including the pressurizing head and the workpieces.
Techniques to control the action of a motor while performing the switching from the feeding action to the pressurizing action in such a manner is disclosed in Patent Literatures 1 and 2. Patent Literature 1 discloses a technique to calculate the ratio of a torque command and a pressure sensor value after a feeding action is performed with position control and to switch the control to a pressure controller when the ratio is stabilized at a constant value. Patent Literature 2 discloses a technique to, when an injection screw of an injection molding machine is the body to be driven, detect a position deviation of the body to be driven with respect to the target position, calculate a first speed command on the basis of the position deviation, and generate a second speed command that corresponds to the target speed of the body to be driven. Patent Literature 2 also discloses a technique to perform proportional integral (PI) compensation processing on an injection pressure deviation to generate a third speed command and select the smallest speed command value from among the first speed command, the second speed command, and the third speed command as the speed command for driving the motor.